Radio wave detector system



Now. 1948. c, s I 2,455,191

mm WAVE DETECTOR SYSTEM Filed Nov. 18, 1944 Alp H Flo INVENTOR CLAUDELANGDCWRICHARDJ.

6C1. 2 AUDIO OUTPUT ATTORNEY.

Patented Nov. 30,1948

PATENT arise RADKO WAVE DETECTOR SYSTEM Claude Langdon Richards, London,England, as signor to The Mullard Radio Valve Company Limited, London,England Application November 18, 1944, Serial No. 564,085 In GreatBritain July 30, 1943 Section 1, Public Law 690, August 8, 1946 Patentexpires July 30, 1963 Claims.

e. g. as amplitude modulation or as frequencymodulation of a carrierwave. It is a feature of the invention that the switch means may beincorporated in the L. F. stage or stages of the circuit. It is moreespecially intended that one of the forms of radiation from which acircuit according to the invention is capable of extracting informationshall be a frequency-modulated carrier wave and for this purpose thecircuit includes discriminator means, preferably arranged in the mannerdescribed in the specification of co-pending patent applicationcurrently filed by me for Frequency'Modulated Receivers", Serial No.564,086, now Patent No. 2,415,656, issued February 11, 1947, accordingto which the output from a limiter is applied to an inductance (primary)which is coupled with another inductance (secondary), the primary or thesecondary or both forming part of a tuned circuit adjusted to theunmodulated carrier frequency, and a connection is provided-between thelimiter output circuit and the secondary circuit whereby a carrierfrequency component from one circuit is added vectorially to a carrierfrequency component from the other circuit, which components are 90 outof phase when the carrier frequency and the tuned circuit (or circuits)are exactly in tune, thephase angle varying on either side of 90 as thecarrier frequency is greater or smaller than the turned frequency theresultant of the components being applied to a rectifier circuitcomprising a single diode. The invention contemplates the use of asingle channel (wholly or in part) for the reception of each of thevarious transmissions which the circuit is capable of receiving, ratherthan the use of separate and distinct channel for each form, and in thisconnection one feature of novelty introduced by the invention comprisesthe application, for the reception of C. W. radiation, of a modulatingvoltage to the anode of a valve which functions as part of the frequencydiscriminating circuit during reception of F. M. radiation. Further,circuits according to the invention may be adapted to provide automaticvolume control; and where they are designed to receive, as one form of 2radiation, a continuous wave transmission, the circuits are arranged sothat a heterodyne beatnote can be applied to the detector withoutinterfering with the A. V. C. provided. It will be noted from thedescription below of forms which the invention may assume that thesevarious" functions are achieved by the use of fewer valves andcomponents than have been necessary in circuits heretofore proposed toprovide some of these functions.

In order that the invention maybe more readily understood certainembodiments thereof will now be described with reference to theaccompanying drawing in which Fig. 1 is a schematic diagram showing oneform of a circuit according to the invention,

Fig. 2 is a schematic diagram showing another form of a circuitaccording to the invention and Fig. 3 is a schematic diagramillustrating a further embodiment of the invention.

In the circuit embodying the invention shown in Fig. 1 the valve V1together with the associated elements Lp,Ls,Cs form alimiter-discriminator circuit for reception of F. M. waves, and issubstantially identical with the circuit described in the aforementionedspecification of co-pending patent application, Serial No. 564,086,now'U. S. Patent 2,415,656, issued February 11, 1947, referred to above.The F. M. waves derived from the preceding stages of the receiver areapplied to a primary widing 8 of a L-F transformer I, the-secondarycircuit 9 of which has one terminal connected to the grid ID of tube V1and the other terminal connected to the cathode II and ground through aresistor 16 shunted by capacitor 17 which resistor effects amplitudelimitingof the- F. M. wave in the tube V1 in know manner. Connected inthe anode circuit of tube Vi is the winding Lp, which winding ismagnetically coupled to the circuits Ls, Cs, tuned to the centerfrequency of the applied wave and is also connected to one end of saidcircuit through capacitor Hi. As pointed out in the above-referred tocopending application, by interconnecting and magnetically coupling thewinding Lp, Ls, a resulting voltage is obtained comprising twocomponents which are in quadrature with respect to each other when theapplied wave has an instantaneous frequency equal to the resonant of thetuned circuit. At frequencies of the applied wave deviating from thecenter frequency, variations'of the relative'phase relationship of thetwo components are produced, thereby correspondingly varying theamplitude of the resultant. The resultant signal is applied to the Athree-way switch 8 has one contact F. M.

connectedto the output of the diode rectiiier oi the tube V1 and theswitch is thrown to this contact when frequency-modulated radiation isbeing received, the impulses being fed through a suitable filter circuitl8, it as shown to the audio output stage of the receiver.

When the circuit is to be used for reception of amplitude modulatedsignals the switch S,is thrown to another contact thereof AM connectedto the gird iii of the pentode in the tube V1. This grid is used as adiode from which A. V. C. and modulated signals are fed through suitablefilter elements 20, 2!, 22, and 23, as shown, respectively to precedingand subsequent stages of the receiver. When the valve is working in thismanner the diode, and the other pentode elements in the tube V1 areinoperative.

For C. W. reception the switch 8 is thrown to the third contact thereof0. W. and a heterodyne signal obtained from a Hartley or otheroscillator formed by the tube V: and the 'tuned circuit 24 is fed bydirect coupling as shown. to the anode i2 oi the tube V1 as a modulatingvoltage. This heterodyne beatnote is rectified in the diode sectionli-ii of the tube V1 and supplied through the selector switch to thelater stages of the receiver. The oscillator tube V:

. .is not in use except for C. W; reception and a switch H (which may bepart of, or ganged to, the switch S) controls the supply of powerthereto. As will be seen no heater current flows to the valve V2 exceptwhen the circuit is used for C. W. reception.

The form of the invention shown in Fig. 2 is substantially identicalwith that shown in Fig. 1 save that for C. W. operation it is preferredto supply the local oscillator voltage to the diode section I 3-i i ofthe discriminator tube V1 through a suitable resistance R and acapacitor 21 rather than by direct coupling to the limiter anode as inFig. 1. For satisfactory operation oi' the discriminator in F. M.reception the tuned circuits L5, Cs must be very heavily damped and theresistance R assists in providing such damping.

A third form of the invention is shown in Fig. 3 Here, for C. W.-operation, the local oscillator voltage developed across a load resistor3i connected to-anode 26 of tube V: is supplied through the intermediaryof a resistor 28 and a capacitor 30 to the control grid of V1 togetherwith the incoming signal. The value oi the voltage from the localoscillator V2 is adjusted (for use during C. W. reception) to be equalto the carrier voltage at which 100% modulation just gives maximum poweroutput. Interference with the A. V. C. operation is prevented by theresistances R1, R2 associated with the positive limiting diode D2.Manual control of the volume maybe effected by means of the variableresistance Ra, operation of which controls both the resultant L. F.signal from the diode D1 and the bias voltage from the oscillator Vi byway ot the diode D3 thereof. The latter voltage is employed as indicatedat G. C. 2 to control in part the gain of the circuit, while asindicated at G. C. I the remainder of the gain is controlledautomatically aspreviously described. It will be noted that variousswitch arms and associated contacts are provided to include or excludevarious parts of the circuit according to the form of modulatedradiation being received, and all may be ganged .-to or term part of theswitch 8 operating as described above. The operation of the variousswitch arms is self-apparent from the drawings and is therefore notdescribed in detail.

I claim:

1. A detector system for a carrier wave havinga predetermined centralfrequency, comprising a discharge tube having a cathode, an anode and acontrol grid interposed between the cathode and the anode, an inputcircuit for the carrier wave connected between the control grid and thecathode, a resistance element and a condenser element connected in shuntwith each other and in series with the control grid and the cathode forproducing grid circuit limiting of the carrier wave and for generating apotential proportional to the amplitude of the carrier wave, atransformer having a primary winding in the output circuit of said anodeand a secondary winding, said secondary winding being tuned tosubstantially the said predetermined frequency and being magneticallycoupled to said primary winding to produce a terminal voltage inquadrature with the voltage of the primary winding, means tointerconnect one end of each of said windings to thereby combine thevoltage of the primary winding and said terminal voltage to produce aresultant voltage, means for rectii'ying said resultant voltage toproduce a potential proportional to the amplitude of said resultantvoltage, a heterodyne oscillator coupled to said discharge tube, meansto energize said discharge tube and said heterodyne oscillator, anoutput circuit, and means to selectively connect the output circuit tosaid means for generating a potential proportional to the amplitude ofthe carrier wave and saidmeans to generate a potential proportional tothe amplitude of said resultant voltage and to selectively energize saidheterodyne oscillator.

2. A detector system for a carrier wave having a predetermined centralfrequency, comprising a discharge tube having a cathode, an anode and acontrol grid interposed between the cathode and the anode, an inputcircuit for the carrier wave connected between the control grid and thecathode. a resistance element and a condenser element connected in shuntwith each other and in series with the control grid and the cathode forproducing grid circuit limiting of the carrier wave and for generating apotential proportional to the amplitude of the carrier wave, atransformer having a primary winding in the output circuit of said anodeand a secondary winding, said secondary Winding being tuned tosubstantially the said predetermined frequency and being magneticallycoupled to said primary winding to produce a terminal voltage inquadrature with the voltage of the primary winding, means tointerconnect one end of each of said windings to thereby combine thevoltage of the primary winding and said terminal voltage to produce aresultant voltage, means for rectifying said resultant voltage toproduce a potential proportional to the amplitude 01' said resultantvoltage, a heterodyne oscillator coupled to the anode of said dischargetube. means to energize said discharge tube and said heterodyneoscillator, an output circuit, and means to selectively connect theoutput circult to said means for generating a potential proportional tothe amplitude of the carrier wave and said means to generate a potentialpropor tional to the amplitude of said resultant voltage and toselectively energize said heterodyne oscillator.

3. A detector system for a carrier wave having a predetermined centralfrequency, comprising a discharge tube having a cathode, an anode and acontrol grid interposed between the cathode and the anode, an inputcircuit for the carrier wave connected between the control grid and thecathode, a resistance element and a condenser element connected in shuntwith each other and in series with the control grid and the cathode forproducing grid circuit limiting of the carrier wave and for generating apotential proportional to the amplitude of the carrier wave, atransformer having a primary winding in the output circuit 01' saidanode and a secondary winding, said secondary winding being tuned tosubstantially the said predetermined frequency and being magneticallycoupled to said primary winding to produce a terminal voltage inquadrature with the voltage of the primary winding, means tointerconnect one end of each of said windings to thereby combine thevoltage of the primary winding and the said terminal voltage to producea resultant voltage, means for rectifying said resultant voltage toproduce a potential proportional to the amplitude of said resultantvoltage, a heterodyne oscillator coupled to the control grid of saiddischarge tube, means to energize said discharge tube and saidheterodyne oscillator, an output circuit, and means to selectivelyconnect the output circuit to said means for generating a potentialproportional to the amplitude of the carrier portional to the amplitudeof said resultant voltage and to selectively energize said heterodyneoscillator.

4. A detector system for a carrier wave having a predetermined centralfrequency, comprising a discharge tube having a cathode, an anode, acontrol grid interposed between the cathode and the anode and a diodeanode, an input circuit for the carrier wave connected between thecontrol grid and the cathode, a resistance element and a condenserelement connected in shunt with each other and in series with thecontrol grid and the cathode for producing grid circuit limiting of thecarrier wave and for generating a potential proportional to theamplitude of the carrier wave, a transformer having a primary winding inthe output circuit oi said anode and a secondary winding, said secondarywinding being tuned to substantially the said predetermined frequencyand being magnetically coupled to said primary winding to produce aterminal voltage in quadrature with the voltage of the primary winding,means to interconnect one end of each of said windings to therebycombine the voltage of the primary winding and said terminal voltage toproduce a resultant voltage, means to connect the 6 other end of thesecondary winding to said diode anode, a load resistance elementinterconnecting the diode anode and the cathode for producing apotential proportional to the amplitude of said.

ant voltage and to selectively energize said het- I erodyne oscillator.

5. A detector system for a carrier wave having a predetermined centralfrequency, comprising a discharge tube having a cathode, an anode, and acontrol grid interposed between the cathode and the anode, an inputcircuit for said carrier wave connected between the control grid and thecathode, a parallel circ'uit arrangement comprising a resistance elementand a capacitive reactance element connected in series with the controlgrid and cathode of said discharge tube to generate a potentialproportional to the amplitude of said carrier wave, a transformer havinga primary winding connected in the output circuit of said anode and asecondary winding, one of said windings being substantially tuned tosaid central frequency and said secondary winding being magneticallycoupled to said primary winding to produce a terminal voltage inquadrature with the voltage across said primary winding, means tointerconnect one end of each of said windings to combine the voltage ofsaid primary winding and said terminal voltage to produce a resultantvoltage, means for rectifying said resultant voltage to generate apotential proportional to the frequency deviations of said carrier wavefrom said central frequency value, an output circuit, and meansselectively to connect said output circuit to said means for generatinga potential proportional to the amplitude of the carrier wave and saidmeans to generate a potential proportional to frequency deviations ofsaid carrier wave.

CLAUDE LANGDON RICHARDS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2, 125,953 Prochnow Aug. 9, 19382, 250, 862 Farrington July'29, 1941 2, 356, 224 Crosby Aug. 22, 1944 2,415, 656 Richards Feb. 11, 1947

